Recognising a Slipping Automatic Gearbox
The engine revs shoot up on pull-away or during a gear change, then the car picks up again after a brief delay or a slight jolt. On the motorway, the rev counter needle can climb without any corresponding increase in speed. The cause depends on the type of gearbox.
Likely Causes by Gearbox Type
| Gearbox Type | Likely Causes |
|---|---|
| Conventional torque-converter automatic (Aisin, ZF…) | Low or burnt fluid, worn internal clutch packs, torque converter |
| Dual-clutch (DSG, S tronic, EDC…) | Worn clutch, insufficient hydraulic pressure (mechatronic unit) |
Why You Shouldn't Wait
In a torque-converter gearbox, every slip heats the internal clutch discs and the fluid. The fluid loses its properties, which causes further slipping — wear then escalates rapidly. In a dual-clutch gearbox, a slipping clutch will eventually put the gearbox into limp-home mode.
Can You Keep Driving?
As little as possible, gently and without towing. If the car can barely move, have it towed rather than forcing it.
Repair or Replace?
On a torque-converter gearbox, a fluid change can help if the fluid is simply degraded, but it will not repair burnt internal clutch packs — in that case, an exchange unit is generally more cost-effective than a rebuild. On a dual-clutch, a clutch kit or a mechatronic unit repair may be sufficient. A reconditioned automatic gearbox is tested and warranted for up to 24 months; for a dual-clutch, it is supplied with a new dual-clutch assembly.
